A Yersinia enterocolitica receptor mutant was isolated which is impaired in ferrichrome uptake. The receptor-encoding gene fcuA was cloned in Escherichia coli K-12. A fcuA mutant of Y. enterocolitica could be complemented by the cloned DNA fragment. The FcuA-encoding region was sequenced and an open reading frame encoding 758 amino acids including a signal sequence of 36 amino acids was found. FcuA shared 34.6% amino acid sequence homology with FatA, the anguibactin receptor of Vibrio anguillarum, but only 20.6% homology with FhuA, the ferrichrome receptor of E. coli. Since the structure of anguibactin differs strongly from that of ferrichrome there seems to be no co-evolution of receptor structure and substrate specificity.
The ferrichrome receptors FcuA from Y. enterocolitica and FhuA from E coli had slightly different substrate specificities. In contrast to FhuA from E coli, FcuA from Y. enterocolitica was more stereoselective and failed to transport enantio ferrichrome. Three additional ferrichrome receptors were cloned from Pantoea agglomerans (formerly Erwinia herbicola), Salmonella paratyphi B and Salmonella typhimurium. Their substrate specificity was similar but not identical.
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